Nuclear warhead monitoring : a study of photon emissions from fission neutron interactions with high explosives as a tool in arms control verification
Name
1021853056-MIT.pdf
Description
Full printable version
Size
2.12 MB
Format
Adobe PDF
Checksum (MD5)
a89bd880a1614a6d9235b98fbe155b38
Author(s)
Snowden, Mareena Robinson
Advisor(s)
Richard C. Lanza and Adam Bernstein.
Alternative Title
Study of photon emissions from fission neutron interactions with high explosives as a tool in arms control verification
Date Issued
2017
Publisher
Massachusetts Institute of Technology
Abstract
Since the signing of the Nuclear Nonproliferation Treaty, the technical community has been working to develop verification options that provide confidence in the reduction or elimination of nuclear warheads, while respecting countries' requirement of limited access to national secrets. This dissertation used a simplified open-source warhead model as a vehicle to investigate the use of secondary gammas, generated passively by neutron interactions inside high explosive (HE), as a signature for the presence of a warhead-like object. Analytical calculations were done to estimate the detectability of radiative capture and inelastic scatter emissions generated within the warhead model. Results showed the emission of gammas from nitrogen, between 5-7 MeV, to be detectable above background with dwell-times exceeding 90 minutes. These calculations motivated the systematic study of the signal experimentally using surrogate materials to represent the warhead's weapons-grade plutonium and HE. The experiment did not show the expected signals. This motivated a simulation of the mock-up experiment using the radiation transport code MCNP6 to help understand the observed results. The experimental and simulation data suggest that correlated backgrounds from neutron interactions with environmental materials dominate the signal. This finding helped provide a basis for understanding the feasibility and challenges to detecting this neutron-induced gamma signal. Three sets of pulse-height spectra have been analyzed: experimental spectra that looked at the effect of the HE surrogate on the overall detected counts; simulated spectra that helped to understand the underlying contributors to the observed experimental result; and a data-MCNP6 comparison that assessed the accuracy of the simulated results. Each set contributed to the quantification of detectability for the emissions of interest. The findings suggest the passive detection of the expected high-energy gamma signal is not feasible, unless backgrounds can be better controlled. The difficulty is attributed to low solid-angle coverage of the neutron source by the melamine explosive surrogate, and competing backgrounds produced by neutron-source interactions with surrounding materials. This thesis also examined the benefits and tradeoffs of this particular verification approach by investigating the non-technical context of the verification, such as the preferences of negotiators. The tradeoffs between confidence and intrusiveness highlight the need for technical verification solutions that span the diversity of options. Factors limiting the development of warhead verification systems, from the bias of researchers to issues of classification and sensitive geometries, were discussed.
Description
Thesis: Ph. D., Massachusetts Institute of Technology, Department of Nuclear Science and Engineering, 2017.
This electronic version was submitted by the student author. The certified thesis is available in the Institute Archives and Special Collections.
Cataloged from student-submitted PDF version of thesis.
Includes bibliographical references.
Subjects
Nuclear Science and Engineering.
MIT Department
Massachusetts Institute of Technology. Department of Nuclear Science and Engineering
Terms of Use
MIT theses are protected by copyright. They may be viewed, downloaded, or printed from this source but further reproduction or distribution in any format is prohibited without written permission.
Persistent DSpace Link
